Pump



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Patented Apr. 14, 1942 UNITED STATES PATENT OFFICE."

Alfred C. Sinclair, Memphis, Tenn. Appmt; (Curci-114;. 7

The present invention relates to pumps of the positive displacement type and has for its primary object the provision of anew and improved pump of high efdciency; a pump that may be built at relative low cost, and one capable of delivering a smooth ow of uid which may be used substantially noiselessly at the point oi application.

The pump of the present invention is adapted to be utilized in connection with liquid having lubricating qualities and at medium pressures and fairly large volumes. A pump of the positive displacement type, such as a rotary pump including pistons reciprocable radially by an eccentric, ordinarily comprises a number of pistons, either odd or even, the total discharge of which, while it is relatively constant. pulsates at a rate dependent upon the speed of rotation of `the pump shaft and the number of cylinders. II the. pump comprises an even y number of cylinders, the pulsations, or ripples, per number to the number of cylinders; and pump comprises an odd number of cylinders, greater than one, the pulsations are equal in number to twice the number of cylinders. Generally speaking, the magnitude of the pulsations with odd and even numbers of cylinders isin the relation of one to two; i. e., the magnitude of the pulsations with an even number of cylinders is approximately twice as great as with an odd number of cylinders nearest the even number of cylinders. The greater the number of lcylinders the less the magnitude of each pulsation.

Inmany applications the pulsations, which are only a relatively small percentage of the total output of the pump, are of little or no moment, but in certain applications they become a maior factor. For example,

y actuated hydraulic plunger type elevators the pulsations are apparent to passengers in the elevator cabs as vibration and noise. The vibration and noise are quite disagreeable and in some instances may be even intolerable. Vibration damping means in the delivery line leading from' the pump to the elevator have been found ineffective to reduce the vibration to a point where it is not noticeable.

Pulsations are undesirable also for the reason that they result in a waste o! energy. Pulsations in the flow of liquids produce like pulsations in pressure and the energy absorbed thereby is avoidance of pulsations 'results in a decrease in the amount of energy required to drive the pump.

The present invention of the pump in revolution are equal in 4 if the.

in the operation of directlyhas for one of its pria mary objects the provision `of a new and improved pump of the positive displacement type having a substantially smooth delivery.

A further object provide a new and improved pump of the positive displacement type so constructed and arranged.

that the afore-described pulsations are substantially eliminated to provide a smooth discharge.

A more specific object of the present invention is to provide a new and improved pump in which the discharge passage from the pump is periodically connected to the suction passage, thereby substantially to eliminate the 'pressure pulsations otherwise occurring. compensation of the pulsations in the discharge the sacrice of some efliciency as a deliberate leak is introduced between the discharge and the supply of the p' p. However, as lwill be described hereinafter, the losses resulting from practice of the present invention are only a very small percentage of the of the energy contained therein. vOf course, it inferior arrangements ot parts are used which would result in increased pulsations, the correction will result in a more serious loss in eiliciency. but it should be noted that the mechanical eiliciency of the pump may still be well above that of other types of pumps which are inherently free from pulsations in the delivered iiow.

A further object of the present invention is to provide a pump having a rotary distribution valve adapted selectively to control the connection of the pump cylinders to the suction and discharge passages of the pump and periodically to connect the discharge passage by-pass some o! the duid. the amount of fluid by-passed being maximum when the discharge from the pump cylinders is a maximum.

A further object of the invention is to provide a valve for controlling the by-pass just mentioned corlistructed integrally with the rotary distribution va ve.

A further object of compensate for the duid from the pump by means of a separate valve operated synchronously 'with the pump shaft.

A further object of the present invention is to provide a by-pass controlling valve that is adapted4 to compensate for pulsations varying from a predetermined minimum to a predetermined the present invention is to minimum.`

A further object of the by-pass ycontrolling valve that is adapted to of the present invention is to It should be understood that this manner is obtained only at now of liquid and consequently to the suction passage to pulsations in the delivered invention is to provide compensate for pulsations of a type wherein the pulsation varies from a predetermined minimum to a predetermined maximum, 'then to an inter-` mediate minimum value, then to a predetermined i maximum value, and finally back to the predeter Another object of the present inventief/i to provide a rotary distribution and by-pass controlling valve that is balanced against hydraulic thrust.

A further object of the invention is to provide a rotary distribution and by-pass controlling valve that is balanced against both axial and lateral hydraulic thrust, thereby to prevent rapid wear of the bearing surfaces of the valve and the development of leakage around the valve.

A further object of the present invention is to provide a pump of the type described in which a positive pressure is maintained in the crank case.

' A further object ofthe present invention is t0 provide a new and improved rotarydistribution valve wherein thel above-mentioned hydraulic balance and maintenance of positive pressure is provided for, in part at least, by the valve.

A further and somewhat moregeneral object of the present invention is to provide means preventing .the ingress of air into the crank case around the valve operating shaft, andy thereby prevent the impairment of lubrication of the moving parts of the crank mechanism and to prevent the noisy operation of the pump which may result from permitting air to ind its way into the cylinders through piston' clearances.

A further object of the present invention is to provide a pump construction that permits the use of considerably lighter parts in the construction of the pump without decreasing the factor of safety. This advantage results from the fact that the crank case is maintained at positive pressure. A further object of the invention is so to construct the distribution valve and the passages leading therefrom to the cylinders that substantially all clicking noises'are avoided.

Other objects and advantages of thepresent invention will become apparent from the ensuing description in the course of which reference is had to the accompanying drawings, in which:

Fig. 1 is an axial vertical cross-sectional view through one embodiment of the pump of the present invention (see Fig. 11 for a side elevational view of a similar pump);

Fig. 2 is a transverse view taken. along the line 2-2 of Fig. 1 (this view-is partly in section better to illustrate certain details of construction);

Fig. 3 is an enlarged partial transverse crosssectional view taken along the line 3-9-3 of Fig. 1, illustrating details of the pressure pulsation compensation means of the present invention;

Fig. 4 is a view similar to Fig. 3 taken along the line 4 4 of Fig. l, illustrating certain details of construction of the hydraulic balancing means for the rotary distribution valve; A

Fig. 5 isa view similar to Fig. 4 taken along the line 5 5 of Fig. 1 illustrating further details of'construction of the rotary distribution valve:

Figure 6 is 'a view showing the developed peripheral surface of the distribution valve illustrating further details of construction thereof and particularly the means for balancing the lateral pressures;

Fig. 7 is a chart in which the angular positions of the shaft (and likewise of the rotary distribution valve) are'plotted as the abscissae, and the rates of delivery are plotted as the ordinates and showing the individual output of each cylinder as well as the total output of the pump, which,

in the illustrated embodiment, comprises seven cylinders. The chart also shows the output of the pump when supplied with pulsation compensating means1 of the present invention. The chart is for a pump having a piston connecting rod that is long as compared with the piston stroke;

Fig. 8 is a view similar to that shown in Fig. v7, illustrating the nature of the discharge of a pump having an odd number of cylinders and a connecting rod the length of which is short as compared to the piston stroke;

Fig.,9 is a view similar to Fig. 3 of a modied form of by-pass valve adapted particularly to compensate for pulsations of the type shown in Fig. 8;

Fig. 10 is a view similar y to Fig. 9. illustrating how that modification may be modied to provide compensation for pumps having pulsations of the type shown in Fig. 7,

Fig. 11 is a side elevational view of a pump similar to that shown in the previous figures provided, however, with a further modified means for compensating for the pressure pulsations. In this modication the compensation is provided by a separate valve operated in synchronisnr with the pump shaft and rotary distribution valve and nect the suction and discharge passages of the Pump;

Fig. 12 is a vertical axial cross-sectional view through the valve illustrated in Fig'. 11; and

Fig. 13 is a vertical transverse cross-sectional view taken through the valve along the line I3-I3 of Fig. 11.

The pump of the present invention is' best illustrated, as a whole, in Figs. l and 2 (for a side elevation of a pump having substantially the same external appearance, attention is directed to Fig. 11). It` comprises a stationary crank case I0 that is made liquid tight for a purpose setv feet I6, whereby the pump may be securely at' tached to a suitable base plate or other supporting means.

The pump shaft I8 is rotatably supported in and held against end play by a pair of spaced apart bearings I9 and 20 of a familiar type, mounted respectively in the drive end plate I2 land a radially inwardly extending partition 22 formed centrally of and integrally of the crank case. The pump shaft may be driven by any suitable means, and in Fig. 1 the shaft is -illustrated as driven by a double pulley 24 secured-to the end ofthe shaft projecting beyond end plate I2. Leakage. of uid along the pump shaft is prevented by suitable seals. 25.

The pump comprisesa plurality of cylinders right half of the rotary,

adapted periodically to con-' for the reason, as will be explained more fully hereinafter, that the magnitude ofthe pulsations in pressure is substantially less than when an even number of cylinders is utilized.

The cylinder bores are selectively placed in communication with a delivery chamber 32, or a suction chamber 34, through cored passageways 36 under the control of a full floating, ported rotary distribution valve 38 that is rotated synchronously with the pump shaft- I8. The valve forms one of the more important features of the present invention and will be described in considerable detail hereinafter.

The pump pistons 40 are reciprocated rn their associated cylinders by an eccentric 42 xedly attached to the pump shaft, as by a key. The eccentric is spaced from the end plate I2 by a spacer 43 interposed therebetween and bearing I8. The eccentric is operatively connected to the pistons by a bearing ring assembly, indicated generally by reference character 44, connecting rods 46 and pins 48. The bearing ring assembly corn-v prises a composite eccentric ring 50 rotatable around the eccentric 42. The connecting rods have slipper end portions` 52 that are held in contact with .the outer surface of the eccentric ring by a pair of retainer rings 54 secured to the ring. It may bc seen that the connecting rods are maintained in contact with the eccentric ring but are free to oscillate about the common center of the slipper portions and the eccentric ring.

The eccentric and its associated ring are lubricated .through a conduit 56 leading from Within the interior of the crank case to a at 58, provided on the peripheral surface of the eccentric,

it being contemplated that the fluid circulated by the pump of the present invention be of the type possessing lubricating properties.

In accordance with another of the important features of the present invention, the interior of the crank case is lled vwith the fluid at a pressure that bears a predetermined relation to the delivery pressure of the pump, thereby to enable lighter parts to be used inthe construction of the pump without decreasing the factor of safety and at the same time prevent the ingress of air into` the pump which would, if not prevented from entering the crank case, impair lubrication and result in noisy operation.

The fluid is supplied to the interior of the crank case from the delivery chamber through a small diameter bore 60 formed at the right-hand end of the rotary distribution valve 38 (as viewed in Fig. l), a substantially semicircular channel 62 formed in the right-hand end of the valve, and through openings between the spaced apart balls of the bearing 2l). The pressure is relieved through a variable area pressure relieving groove 64 formed at the reduced end portion 66 of the pump shaft I8, adapted to rotate the rotary distribution valve. This valve is capable of limited sliding movement with respect to the shaft in order that the valve may be balanced againstaxial hydraulic thrust in a manner to be described shortly. When a balance exists, the

groove 64 establishes communication from the interior of the crank case to the suction chamber 34 through an annular space, indicated by the reference character 68, between a hub portion 10 of the rotary valve and a shoulder formed by portion 12 of the shaft and a portion of the bearing 20. By proportioning the areas of the hole 60, groove 64, and the valve surfaces subject to the delivery and discharge pressures, the pressure Within the interior of the crank case may be designed to bear a fixed relationship to the pressure in the discharge chamber.

A decided advantage in economy of material is secured by maintaining a positive crank case pressure. During the upstroke of each piston full delivery pressure is exerted upon the piston head, thereby determining the thrust which would have to be carried byl the piston pin and the connecting rod slipper. However, the crank case pressure is exerted on the underside of each piston, thereby to reduce the thrust in the same proportion that the crank case pressure bears to the delivery pressure. The. pistons and rods of the cylinders performing their suction strokes at this time are, of course, subject to a tension due to the crank case pressure, whereas they would otherwise be practically without load. However, the bearing loads so created will not exceed those produced on the delivery stroke. The result is to reduce, by as much as desired up to one half, the maximum load on each piston pin and connecting rod, thereby allowing lighter parts tol selectively to connect the cylinders to the discharge and suction chambers 32 and 34, respectively, is keyed to the reduced end portion 66 of shaft I8 by a key 13 so constructed and arranged with respect to the shaft and valve that the latteris free to move endwise of the shaft a limited extent, as previously mentioned. The valve is journaled for rotation in a pair of bushings 16 and 18, and the large end of the valve (the right end as viewed in Fig. 1) is fitted closely within the bushing 16. The latter is provided with a series of spaced apart ports coinciding with the openings in the passageways 36 giving the latter access to the valve. The large end of the valve is also provided with two identical oppositely located ports 82 and 84, respectively, the suction and discharge ports (see Fig. 6), separated by solid portions 86 and 88 each of a length sufficient to cover one port in the bushing 16 with a slight overlap.

In order to prevent the too sudden admission and cut off of fluid and the resulting clicking sound, the ends of the ports 80 are preferably rounded or pointed, as indicated by reference character 90.

Fluid is supplied to the suction chamber 34 of the pump through an inlet passage comprising a pipe 92 threaded into the end plate I4 concentrically with respectto and opening directly into the suction chamber 34. The discharge passage comprises a pipe 94 threaded into a suitably located hole in the crank case. In the illustrated embodiment the discharge passage is shown on the under side of the pump, but it should be understood the pipe may be located wherever deu its downstroke, the corresponding port 36 is just opened to the suction chamber 34 by the suc- -it may be seen that Y, combine to produce revolution of the tion port 82 and as the piston attains its maximum velocity, the -port is fully opened to the suction chamber, .and as the piston reaches the bottom of its stroke the port is just closed. Fur-l ther rotation of the shaft causes the piston to ascend in the cylinder and-at the same time the rotation of the distribution valve 38 opens a passage from port 36 to the discharge port 84 in the valve, thereby to connect that port with the discharge chamber 32. Each cylinder is alternately connected to the suction and discharge chambers and the construction of the valve is such that at least three cylinders are open .to each of the chambers at any one time.

Before proceeding further with a detailed discussion of the pump of the present invention, it is deemed-advisable to consider the nature of the discharge from a pump of this type to bring out more clearly the disadvantages of the pumps now known to the art and thereafter to point out how these disadvantages are overcome.

Referring now to the chart shown in Fig. 7, the discharges of the seven separate cylinders of the pump described above a totaldischarge ow that when the shaft is driven at Each cylinder discharges duris nearly uniform, a constant-speed. ing one-half of'a overlap in the manner shown in thev chart of Fig. 7, where the discharge from each cylinder during one rotation of the pump shaft is indicated by thel substantially -sinusoidal curves marked numbers I to 1, inclusive. 'I'he summation of the output of the individual cylinders gives the total output of the pump, as indicated by reference character 8. This curve shows that there'are two ripples 9 for each cylinder per pump shaft, which is the case with pumps having an odd number of cylinders greater than one. As previously mentioned, when the number of cylinders is an even one, there 'are as many ripples as cylinders, but the magnitudeof the ripples is about twice as; great.

The minimum delivery Il, to which a value of 100% has been arbitrarily assigned, is only about 2.6% less than the maximum delivery. The diagram shown in Fig. 7 is illustrative of a pump having connecting roQds that are very long compared with the stroke of the pump. Where the connecting rods are relatively short compared with the stroke of the pump, the total output curve is somewhat different, as shown in Fig. 8.

For many purposes the pulsations in the discharge of the pump are not of particular importance, and the amount of variation may be reduced by increasing the number of cylinders and by using an odd number of cylinders. For certain purposes, as for operating directly actuated plunger hydraulic elevators, the pulsations in the discharge of the pump are apparent in the elevator cab as a vibration and noise which disagreeable and oftentimes intolerable Damping devices installed in the delivery ,line are found to be ineffective as a means-of re-V ducing this vibration to a desired minimum.

To provide an economical as well as thoroughly satisfactory means for avoiding the pulsations referred to and form discharge, the pump of the the pulsations are eliminated 4in present invention by periodically bi1-passing a portion of the fluid from the discharge chamber 32 into the suction chamber 34, the period between by-passes being so arranged that they correspond 4to the ripples in the outrevolution, and the discharges to provide a substantially uni put ofthe pump, and the amount being so regulated as to correspond to the magnitude thereof.

While this arrangement for smoothing the discharge of the pump entails a sacrifice of some efficiency, as a deliberate leak is introduced between the discharge and suction chambers of the pump; the loss is only a very small percentage of the total now. In the chart shown in Fig. 7 the loss is only about 11/2% of the pump output with a corresponding energy loss. However, the mechanical efllciency of the pump may still be wellabove that of other types o1' pumps which are inherently free from pulsations in the delivered flow.

Referring now more particularly to Figs. 1 and 3, it may be seen that the is adapted periodically to be connected to the suction chamber through a small diameter hole |00 extending through an internal boss |02 formed integrally with end plate I4 and through the valve bushing 18 (which is mounted in the boss) and through one of fourteen small diameter holes |04 vthrough the left end of the rotary distribution valve 38, depending upon the posi tion of the pump shaft and valve. 'I'he hole |00, extending through the boss opens into a groove |06 having a vertical crosssection of men'iscus shape for the purpose o1' making the by-pass passage of a shape to produce a by-pass corresponding to theshape of the pulsation. The hole |00 and groove |06 are so located as to be entirely closed by the portions of the valve between theholes |04 of the latter when a piston is at its upper or lower dead center, that is, when the output of the pump is at one of its minimum points.

Theaction of the by-pass valve is to produce a leak from the discharge chamber into thel sucunscrewed. 1 The exact size of the bleed holes |00 and |04 `aswell as the shape of the groove |06 may best be determined by trial for the particular combinasures-ordinarily required in an installation.

When the effective length of the connecting rods is short, as compared with the stroke of a' cylinder, it may occur that this method of comdischarges. charge in a discharge chamberY |02 and bushing 18,

The result le a f that is balanced against both perceptively greater than the minimum occurring as each cylinder is at bottom dead center--subi stantially as shown in Fig. 8. Referring now to this gure, which illustrates only a portion of a curve silimar to that shown in Fig. 7 with exception that the individual cylinder discharge curves are not shown and, instead of illustrating a pump having a specific number of cylinders, the number of cylinders has been generalized. From this it may be seen that the number ofripples 9 is equal to twice the number of cylinders per revolution of the pump shaft and that the first-mentioned minimum values -(a and e in Fig. 8) are spaced apart a distance equal to l/n revolution as are the second-mentioned minimum values- (c in Fig. 8), whereas the latter are spaced a distancew1/2n revolution from the former.

To compensate for pulsations of the type illustrated in Fig. 8, the construction illustrated in Fig. 9 is utilized. The valve 38 is provided only with a number of holes equal to the number of cylinders, in this case seven, indicated by the reference -characters |20 of a diameter h. Two holes |22 vare drilled through the bearing bushing 18 andthe boss |02 formed integrally with the end plates |4. They are spaced apart a distance equal to one-half the distance between adjacent holes |20 in the bearing and open into grooves |24 having a cross-section that is meniscus shaped. The grooves |24 are so spaced that their outer ends reach from one hole to another without opening either. Thus, when the discharge from the pump is at a minimum (point a. Fig. 8) asy one piston is at its bottom dead center, there is no leakage -through holes |20 and |22. As the discharge increases to a maximum (point b Fig. 8), the flow through a pair of holes |20 and .|22 becomes a maximum. As the flow reaches the '25 muy urge the valve to the right.

second minimum point (point c Fig. 8). the

grooves |24 only partly cover a hole |20 and sufiicient ow occurs to neutralize the difference between the ordinates of points a and c. In this manner complete compensation may be secured in spite of the irregularities of discharge and a smooth uniform ow corresponding to the line (marked 100%) in Fig. 8 is obtained. y

The last-described compensation arrangement may be modified to provide compensation for pulsations occurring when the length of the connecting rod is great enough to produce a discharge similar to that shown in the chart of Fig. 7.` This modification, which isshown in Fig. 10, possesses the advantage that it requires less drill` ing than that first described.

Referring now to Fig. 10, it may be seen that the distribution valve 38 is provided with seven equally spaced holes |30 just as in the modification of Fig. 9, and that bushing 18 and boss |02 are likewise provided with a pair of holes |32 spaced apart as described in the last-mentioned modification and opening into the meniscus shaped cross-section The grooves |34 are so spaced apart that the portion of the bearing bushing 18, indicated by reference characters |88, is wide enough to cover a hole |30. It may be seen that by this arrangement the leakage pulsations are all alike and therefore compensate for the type of ripples disclosed in the ychart of Fig. '7.

Another of the primary features of the present invention is the provision of a distribution valve axial and lateral (or radial) hydraulic thrust, thereby to provide age at these surfaces. yThe means for providing the axial balance also serves to maintain the positive pressures in the crank case previously described but it may be utilized independently of this feature, if desired, as by utilizing a separate chamber in place of the crank case. This means comprises the constant area orifice or passage from the discharge chamber to the interior of the crank case and the variable area orice or passage 84-88 from the interior of the crank case to the suction chamber 34, and includes the proper dimensioning of the axial cross-section areas of the valve subject to the discharge and crank case pressures. The ratio between the areas of the orifices determines the ratio between the pressure differences from the discharge chamber to the crank case and from the crank case to the suction chamber.

Referring now to Fig. 1, it may be'seen that the entire right end of the valve as viewed in this figure (the larger end) maybe considered as a piston subject to crank case pressure, which pressure tends to shift the valve to the left. The left end (the smaller end) of the valve, forms a piston subject to the suction pressure, which is substanzero. The difference between the areas of the two ends is subject to the pressure existing in the delivery chamber, which pressure tends-to It may be seen that the ratio of the area of the right end of the valve to the difference in areas of right and left ends,

Vmust be the same as the ratio between the discharge and crank case pressures in order for the valve to be in axial equilibrium.

y If the valve be assumed to be in the extreme right-hand position, the hub portion 10 thereof closes the passage 88 and iiuid under pressure may enter the crank case from the discharge chamber through the passage 60. Under these circumstances the pressure in the crank case tends to increase until it equals that in the discharge chamber. However, as soon as the crank case pressure` becomes great enough, the thrust nally grooves |34 of and less likelihood of the development of leakagainst the entire area of the right end of the valve overbalances the opposite thrust due to delivery pressurev against'the smaller area exposed thereto and the valve is moved to the left uncovering a portion of the groove 64. The valve takes a position such that .the opposing thrusts are equal, at which time the pressure on each area multiplied by the area against which the pressure acts, are equal, and the relation between discharge and crank case pressures set forth, will exist.- It may be seen that exact axial balance is obtained and that any fractional part of the discharge pressure that may be desired can be maintained within the crank case by properly proportioning the cross-sectionareas of the valve at its ends.

The valve is balanced against lateral (or ra-- dial) hydraulic thrust, which resultsfrom the fact that different pressures exist in the opposite ports 38 at any one time, by opposed balancing 38 is provided with a pair of balance recesses |40 and |42 oppositeiy located with respect to each other and communicating with the dis-4 charge and suction chambers respectively, by passages |44 and |46, as best shown in Figs. 4 and 6. To equalize the pressures over the bear` ing area nearest the discharge chamber 32, an annular groove |48 is utilized (see Figs. 1 and 6).

,The areas of the balance recesses may be made equal on opposite halves of the valve and when this equality is attained there can be no unbalanced lateral pressures tending to force the valve to one side or the other at any suction or delivery pressures.

' Proper dynamic balance of the pump, in part at least, is obtained by making the large end of the valve heavier on the side opposite the high point of the eccentric. This is accomplished by cutting away a portion of the valve end to provide thel substantially semicircular groove 62 which lies, as may be seen from Fig. 4 and a comparison of this ligure with Fig. 1, at the same side of the shaft as the high point of the eccentric. It may be noted that the balance Weight afforded by the valve construction is symmetrically located with respect to the plane of the cylinders.

In the embodiment illustrated, if the enlargement of the valve is not suicient tocompensate fully for the dynamic balance, additional compensation may be effected by mounting a balance weight |50 to the driving pulley 24.

Before proceeding with a detailed description of the operation of the pump and the modifica,- tions of the pulsation compensating means described above, it is deemed best to describe a further modification of the compensating means. In the compensating means heretofore-described,

' the discharge chamber is connected periodically to the suction chamber, but equally good results may be obtained by connecting the suction passage to the discharge passage and -utilizing a separate valve driven synchronously with the pump for the purpose of periodically connecting the two passages, thereby to eliminate the undesirable pulsations. Aconstruction of this nature is illustrated in Figs. 1l, 12, and 13.

The pulsation compensating valve, indicated generally by reference character |52, is adapted periodically to connect the discharge and suction passages- |54 and |56 through a pair of small diameter tubes l| 58 and |68, thereby to by-pass an amount of the pumped fluid to eliminate the pulsations in the pump delivery. The valve may be, and is shown, mounted separately 'from the pump upon a standard |62, to which it is suitably secured, as by bolts.

The valve is rotated in synchronism with the pump shaft and distribution valve by a pair of gears |64 and |66, the former of which is mounted on the pump shaft and the latter affixed to a shaft |68 one end of which forms the moving part of the valve.

The valve proper comprises a valve chamber |10 within which rotates the aforesaid end of shaft |68. This end of the shaft is provided with opposed grooves |12 interconnected by a ysmall diameter hole |14. The grooves |12 are of a shape to form part of the shaft with a substantially elliptical cross-section, as indicated by the reference character |16 in Fig. 13, and the hole |14 extends through the short diameter portion of the ellipse. The valve chamber is connected to the tubes |58 and 68 by small holes |18 and |80 and nipples |82 and |84, respectively.

Leakage -of fluid from the valve along the shaft |68 is prevented by a gasket |86 held in place by an adjustable clamping member |88.

In order to compensate for the pulsations of the type illustrated in the chart of Fig. '1, it is necessary that' the rotary portion of the valve rotate at a speed seven times that of the pump lution of the shaft and the valve isso constructed that the discharge passage is connected to the suction passage twice per revolution of the rotary portion of the valve. .l v

The shape of the valve is sov designed as to provide a leakage that corresponds substantially to the shape of the ripples so that the ripples are substantially entirely eliminated to give a uniform pump output, the elliptical cross-section portion |16 providing for the gradual increase and decrease in the amount of the fluid bypassed.

Reviewing now the operation of the pump and the modifications thereof described above, it is assumed irst that the pump is driven at a constant speed from a suitable prime mover connected to the pulley 24. Rotation of the pump shaft effects reciprocation of the seven pistons of the pump and the cylinders are .selectively connected to the suction and discharge chambers by means, of the rotary distribution valve in a manner that it is believed to be clear from the preceding description.

The pump, if not `"compensating means of the present invention, would have an output o1' the character indicated by reference character 8 in Fig. '1. each time that a piston reaches its maximum velocity position whereat the pump output is a maximum, the discharge chamber is connected to the suction chamber through a by-pass passage. However, as the output of the pump increases from a minimum value to a value, a gradually increasing amount put is by-passed from the discharge of the out- A pump of light construction and one that operates in noiseless manner is obtained by maintaining a reduced but positive pressure within the crank case by connecting the latter to the discharge and suction chambers through orifices of different cross-section areas.

The rotary distribution valve is hydraulically balanced against axial and lateral pressures. It is balanced against axial pressures by connecting the portions thereof subject to the pressures in the delivery and suction chambers 32 and 34 to the interior of the crank case through the variable area orifice 64-68 and the constant area orifice 60 and by constructing the said portions of the valve with predetermined areas. The various orifices and the balancing action have been described in the preceding portion of the specification and it is not deemed necessary that 'the description be repeatedfat this point. The

` effect further balancing, a portion ofthe valve ize pressures thereabout.

The pump is dynamically balanced by making is provided with the annular groove |48 to equalthe rotary distribution valve heavier on the side provided with the pulsation maximum to the suction chamber, the amount being just enough to opposite the high point. of the eccentric 42 and by adding a suitable balance weight |50 to the pulley 2l also as described above.

All the rotating parts of the pump are readily lubricated bythe' pump fiuid itself which possesses lubricating qualities. The interior of the crank case is filled with the fluid and consequently all the bearings and bearing surfaces are lubricated. The eccentric ring is lubricated through the passage 56 and upon the surface of the eccentric l2.

If the pump is constructed so as to have an output of the character illustratedyin the chart of Fig. 8, then the construction of the rotary distribution valve is modified to conform with the construction illustrated in Fig. 9. This construction, it will be recalled, provides for the' compensation of ripples having alternate minimum values that are different from .each other. The compensating means disclosed in Fig. may be utilized in place of that disclosed in Figs. 1 to 6. The modification of Fig. 10 eliminates a number of drilling operations as the rotary valve requires only as many holes as there are cylinders and is preferable for this reason.

As indicated above, it is not necessary that the rotary distribution valve be constructed to provide the necessary by-passing of liquid from thedischarge to the suction side to effect compensation of the pulsations. As a matter of fact,

the valve may be entirely separate from the pump and a modification of this'nature has been described above in connection with Fig. 11. The valve comprises a rotary valve member having a single passage therethrough and adapted to connect the discharge to the suction passage twice for every revolution of the valve. The valve is driven in synchronism with the pump shaft at a speed such that the discharge .side is connected to the suction side of theV pump the necessary number of times to effect the desired compensation.

Other modifications of the presentinvention will suggest themselves to those skilled in the art and it is contemplated that the above described embodiments are descriptive and not limitative in character.

What I claim as new and desire to secure Vby United States Letters Patent is as follows:

1. In combination, a pump of the positive displacement type having a pulsatory discharge characterized by periodic pressure peaks above a uniform value, a suction passage therefor, a discharge passage therefor, and means connecting the discharge to the suction passage in synchronism with and during the pressure peak periods for effecting flow from the discharge to the suction passage in quantities to effect a substantially uniform discharge.

2. In combination, a pump of the positive displacement type having a pulsatoryV discharge characterized by periodic pressure peaks above a uniform value, a suction passage therefor, a discharge passage therefor, means including a passage connecting the discharge to the suction passage and means for opening said passage in synchronism with and during the pressure peak periods for effecting fiow from the discharge to the suction passage in quantities to effect a substantially uniform discharge, and adjustable means for varying the effective cross-section area of saidperiodically openedv passage.

3. In combination, a pump of the positive displacement type, including stationary and movable portions and means for imparting relative the at 58 providedy charge to the suction passage in synchronism' with and during the pressure peak periods for effecting flow from the discharge to the suction passage in quantities to effect a substantially uniform discharge.

4. In combination, a pump of the positive displacement type including a plurality of cylinders and pistons and means for imparting relative movement thereto, wherein the discharge of the pump is pulsatory in nature and characterized by periods of peak pressures, a suction chamber, a discharge chamber, a rotary distribution valve having a pair of opposed ports for operatively connecting said pistons to the suction and discharge chambers in proper time relationship with respect to the relative movement of the pistons and cylinders, a restricted opening leading from one of the chambers to the valve, land a plurality of openings through said valve to the other of said chambers, said openings being so located that they are connected to the restricted opening at least during the pressure peaks whereby the two chambers are periodically interconnected to compensate for the pulsations.

5. In combination, a pump of the positive displacement type including an odd number of relatively movable cylinders and pistons4 and a drive shaft for effecting relative movement thereof, a suction chamber located substantially in alignment with the shaft and spaced from one end thereof, a discharge chamber substantially concentric to said suction chamber, a rotary distribution valve separating the two' chambers and mounted within the pump for rotation by said i number of the cylinders to the discharge chamber, the discharge from the cylindersA to the discharge chamber being pulsatory in nature and the number of pulsations being twice the number of cylinders per revolution of the pump shaft, a passageway of relatively small cross section area leading from the discharge chamber to the valve, said passageway terminating in a meniscus-shaped groove, a plurality of small cross section area passageways equal in number to the number of pulsations extending through the valve, said last-mentioned passageways being equally spaced around the valve, the space between adjacent passageways being sufficient to close the meniscus-shapedgroove, and the valve being so located with respect to the pump shaft and first-mentioned passageway that the latter is closed whenever the .relative movement between a cylinder and its associated piston is substantially zero. y

6. In combination, a pump of the positive displacement type including a plurality of lcylinders and pistons and means for. imparting relative movement thereto, wherein the pump discharge is pulsatory in nature and the number of pulsations is twice the number of cylinders per cycle, a suction chamber, a discharge chamber, a rotary distribution valve having a pair of opposed ports for alternately connecting said cylinders to the suction and discharge chambers in propertime relationship to the movement of the pistons, a

' shaft for effecting relative movement thereof, a

suction chamber located substantially in alignment with the shaft and spaced from one end thereof, a discharge chamber substantially concentric to said suction chamber, a rotary distribution valve mounted within'the pump for rotation by said one end of the shaft, said valve having' a pair of opposed ports, one forsimultaneously connecting several of the cylinders to the suction cliamber and the other for similarly connecting an equal number of the cylinders to the discharge chamber, the total discharge from the cylinders to the discharge chamber being pulsatory in nature and the number of pulsations being twice the number of cylinders per revolution of the pump shaft, a pair of relatively small diameter passageways leading from the discharge chamber to the valve surface and terminating in meniscus-shaped grooves, said passageways being spaced apart an angular distance equal to half the angular distance between adjacent cylinders, grooves being spaced apart a distance suflicient to close hereinafter-mentioned passageways through the valve, small diameter passageways equal in number to the number of cylinders extending through the valve, said passageways be-` ing equally spaced around the valve, the space between adjacent passageways being suiiicient to close both the meniscus-shaped grooves, and the valvev being so located with respect to the pump shaft and first-mentioned passageways that the latter are closed whenever a cylinder and piston are at one of the two positions at which the relative movement therebetween is substantially zero.

8. In combination, a pump of the positive displacement type, including a plurality of cylin- --ders and pistons and means for imparting relative movement thereto,`wherein the pump discharge .is pulsatory in nature and the alternate pulsations have different minimum values, a suction chamber, a discharge chamber, a rotary distribution valve having a pair of opposed ports for alternately connecting saidl cylinders to the suction and discharge chambers in proper time relationship to the movement of the pistons, a pair of relatively. small' diameter passagewaysleading from one of the chambers to the valve, said passageways terminating in meniscusshaped grooves, the adjacent ends of which meet substantially at the valve surface, and a plurality of openings through said valve to the other of said chambers, said openings being so located with respect to each other and the passageways that the two chambers are interconnected to each other in synchronism with the pulsations and the openings are in substantial alignment with the meeting ends of the grooves when the pulsation is at the higher of the minimum values.

9. In combination, a pump of the positive displacement type including a number of relatively and the adjacent ends of the effecting relative movement thereof, a suction chamber, a discharge chamber, a distribution valve mountedfor rotation withinthe pump by said drive shaft, said valve having a pair of vopposed ports, one for simultaneously connecting several of the cylinders to the suction chamber and the other for similarly connecting an equal number of the cylinders to the discharge chamber, .the cylinders. pistons, driving means and distribution valve being so arranged with respect to each other that the total discharge from the cylinders is pulsatory in nature, and' alternate ,pulsations ,have different minimum values, the number of pulsations per revolution .of the shaft being dependent upon the number of cylinders utilized, a pair of passageways of relatively small diameter leading from the discharge chamber to the valve surface, said passageways terminating in a pair of meniscus-shaped grooves, the adjacent ends of,which meet substantially at the valve surface, a plurality of small diameter passageways equal in number to the number ofpulsations extending through the valve, the space between adjacent passageways being suiiicient to close both the meniscusshaped grooves, and said valve and said pair of small diameter passageways being so constructed and arranged with respect to the rotary distribution valve and relatively movable pistons and cylinders that the pair of vsmall diameter passageways are closed when the total discharge from the pump is at the lower of said two minimum values, and the stantially centrally of one of the passageways in the valve when the total discharge is at the other 'of said minimum values.

means including a relatively small conduit and a rotary valve mounted separately from the motor and driven by the motor for connecting the conduits in synchronism with and during the pressure peak periods for effecting flow from the movable cylinders and pistons and means for Y discharge to the'suction chamber' inrquantities to effect a substantially uniform discharge.

1l. In combination, 4a pump having a crank vcase and pistonsand cylinders relatively movable to each other therein, shaft for eecting relative means including a movement between the pistons and cylinders, suction and discharge passages, a valve rotatable by said shaft for alternately connecting the cylinders to the passages, saidv valve having bearing surfaces at its ends and suction and discharge ports intermediate its'ends, bearings for the end portions of said valve, and means including passageways in the valve and one of said' bearings for periodically interconnecting the suction and discharge passages.

12. In combination, a pump of the positive displacement type, having a pulsatory discharge characterized by periodic pressure peaks above a uniform value, a discharge passage therefor,

and means operable in synchronism with and during the pressure peak periods for relieving the pressure in said passage in quantities to effect a substantially uniform discharge.

` ALFRED C. SINCLAIR.

point at which thev -meniscus-shaped grooves meet is located subhaving a pulsatory discharge 

